Beer and related alcoholic beverages in draft form are usually conveyed in pipes or ducts from a supply, such as a keg to an outlet for dispensing purposes. Such arrangements are common in hotel and associated industries where beer is supplied in a pipeline conveyed to a tap located adjacent a bar. Ducts or pipes which carry such beverages tend to require regular cleaning because of bacteriological build-up within the pipes or ducts. This is normally a tedious task requiring disassembly of the pipelines and cleaning by passing a cleaning or flushing fluid therethrough. This also incurs a cost which is passed onto the consumer.
Particular bacteria which create spoilage problems in beer and related alcoholic products include:
______________________________________ Serratia spp Pseudomonas spp Achromobactger spp Acetobacter spp Flavobacterium spp Obesobacterium spp Lactobacillus spp Pediococcus spp Leuconostoc spp Aeromonas spp ______________________________________
The Yeast spp include:
______________________________________ Saccharromyces spp (wild types) Schizosaccharromyces spp Toropulis spp Klueverkia spp ______________________________________
Bacteria together with the blue-green algae and the Archaebacteria comprise the `Procaryotes` (or Procaryotic organisms). Yeast, and plants and animals, comprise the `Eucaryotes` (or Eucaryotic organisms).
Bacterial and yeast cells transfer nutrients across a cytoplasmic membrane which is the "selective permeability membrane" between the cell cytoplasm (interior) and the external environment. The supporting cell wall is somewhat porous and acts as a sieve only to exclude molecules larger than about one nanometer. Certain enzymes, and especially the electron transport chain, that are located in the membrane, are responsible for an elaborate active transport system which utilises the electrochemical potential of the proton to power it.
Growth for unicellular organisms implicitly includes the potential for asexual reproduction, or increase in cell numbers (or biomass). The determinants of microbial growth are described as consumable and environmental. Consumables represent the essential food, or nutritional requirements of cells. Conventionally they include sugars, starches, protein, vitamins, trace elements, oxygen, and carbon dioxide but bacteria are the ultimate omnivores, and substrates as diverse as plastic, rubber, kerosene and cement can be subject to microbial attack. Environmental determinate are those limiting growth factors, the main being pH, temperature and water availability. Most bacteria grow best between ph 7.4 to 7.6, however, the range is extreme form some species, and some exception bacteria can grow at pH 1-2, while others exist at pH 9-10.
The growth requirements outlined above express themselves as growth through the less tangible but fundamental necessity of energy transfer, which is provided by metabolism. Living cells need a system of energy storage and this is provided by chemical bond energy, strictly the free energy of hydrolysis of a diphosphate bond in the compound ATP--adenosine triphosphate. Energy yielding reactions and energy storage systems form a common pattern found in all living systems. A fundamental characteristic of these reactions is that they proceed via a series of steps each mediated by a separate enzyme. This ensures a gentle transfer of energy, not an explosive energy release.
The majority of bacterial and fungal cells do not colonise aqueous systems as free swimming entities but selectively colonise the water/surface interface layers. Thus they bind to these interface layers in a biofilm.